1. Field of the Invention
The present invention relates generally to systems for operating, stabilizing and/or controlling tunable light sources, for use for example in communications systems. The present invention also relates to a digital software-based system with multiple control loops for controlling a laser device, such as a distributed Bragg reflector (DBR) device.
2. Description of the Related Art
Analog-based systems, with ultra-fast control loops operating inside of other loops, have been suggested for use in controlling DBR laser devices. Such analog-based systems lack the flexibility of digital control systems, however. Moreover, the analog-based systems do not provide the ability to fully automate the control process via operating software.
Multi-parameter control (wavelength, mode-hop avoidance, power and optical amplifier gain) of DBR lasers presents two fundamental problems. The first is that, to mode-stabilize a DBR device, the output from the backface must be monitored during ramping of the current to the tuning section. The ramping of the tuning current tends to alter the output wavelength, which is undesirable. The other problem is that ramping of the tuning current affects the amplitude detected by the backface monitor. The characteristics of these changes are fundamental to proper mode stabilization. Any changes, either deliberate or due to aging effects, in the current to the gain section of the device will also produce changes at the backface that could be interpreted as actual changes in the tuning section. There is a need in the art for a digital feedback control system, with nesting and interaction between the various control functions, that can provide a complete DBR operating control solution.